| Erhai lake is the second largest freshwater lake in Yunnan province, and it plays an important part in water-supply, irrigation and drainage, generating electricity, climate regulation, fishery, transportation and tour to local people. Becaues of excess use of natural resource and pollution from human activities, it is in the key point of eutrophication process.In this paper, the eutrophication models of lakes and reservoir were widely reviewed, especially the AQUATOX model——a process-based ecological model. Based on the experimental data and water quality data (2007-2009), AQUATOX model was applied in this study to settle a set of parameters applicable for the Erhai-ecosystem, validate the simulation result, and investigate the response of eutrophic state to nutrient input in Erhai Lake combining with quantile regression analysis.The main works are outlined as the following:Through the establishment of AQUATOX ecological model in Erhai lake, considering the load into the lake, light, temperature, wind, rainfall and other hydro-meteorological conditions and plankton growth of algae in the lake.Then, combine with experiment and reference, sensitivity analysis method was used to calibrate the model parameters, which makes the simulation results more accurately reflect the actual situation of eutrophication in Erhai Lake.This study simulated the routine water quality dynamic and the annul succession of algae. Though there is a little difference in the trend of TP with measured data changing; ph, water-temperature, TN and Chla concentration were all well coincide with measured data. The succession of Diatom to Blue-green alga during the season was also described in the results, and Blue-green alga was showed as the dominant algae in the system.Both statistics analysis method and model simulation method are implemented to study on Effect of nutrients input (Nitrogen and Phosphorus) on Algal Growth in Erhai lake. The results exhibited that Erhai-ecosystem is sensitive to the nutrient input, and has a good response to that change.When Chla concentration is high than10μg/l, TN and TP both plays a linear regression relation with Chla,whle TP has a better coefficient of determination.It suits with simulation result which shows TN and TP are both limiting factors.Furthermore, when increasing output nutrient loadings,TP plays a better enhancing-effect to Chla concetration than TN; while in decreasing control, TN shows a better reducing-effect to Chla concetration than TN. There is an enhanced coordinated effect in Chla concetration when regulate TN and TP at the same time.When chla concentration is under7μg/l in Erhai Lake, as in a oligotrophic state, only TN shows a linear regression relation with Chla. If the TN concentration is kept or under the threshold of0.26mg/L, which means to cut the TN input more than43.3%as before, the eutrophication process can well be restrained with a change in the dominant algal specie and a sharp fall of Chla concentration,then TN is the limiting factor.Finally, Different scene were settled, like inertia development,drought threaten and four schemes for the planning target, to provide technical and academic support for the the control of eutrophication In Erhai Lake... |
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